Pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: A review

Biofuels produced from various lignocellulosic materials, such as wood, agricultural, or forest residues, have the potential to be a valuable substitute for, or complement to, gasoline. Many physicochemical structural and compositional factors hinder the hydrolysis of cellulose present in biomass to sugars and other organic compounds that can later be converted to fuels. The goal of pretreatment is to make the cellulose accessible to hydrolysis for conversion to fuels. Various pretreatment techniques change the physical and chemical structure of the lignocellulosic biomass and improve hydrolysis rates. During the past few years a large number of pretreatment methods have been developed, including alkali treatment, ammonia explosion, and others. Many methods have been shown to result in high sugar yields, above 90% of the theoretical yield for lignocellulosic biomasses such as woods, grasses, corn, and so on. In this review, we discuss the various pretreatment process methods and the recent literature that...

http://ucce.ucdavis.edu/files/datastore/234-1388.pdf

Methods for Pretreatment of Lignocellulosic Biomass for Efficient Hydrolysis and Biofuel Production

Lignocelluloses are often a major or sometimes the sole components of different waste streams from various industries, forestry, agriculture and municipalities. Hydrolysis of these materials is the first step for either digestion to biogas (methane) or fermentation to ethanol. However, enzymatic hydrolysis of lignocelluloses with no pretreatment is usually not so effective because of high stability of the materials to enzymatic or bacterial attacks. The present work is dedicated to reviewing the methods that have been studied for pretreatment of lignocellulosic wastes for conversion to ethanol or biogas. Effective parameters in pretreatment of lignocelluloses, such as crystallinity, accessible surface area, and protection by lignin and hemicellulose are described first. Then, several pretreatment methods are discussed and their effects on improvement in ethanol and/or biogas production are described. They include milling, irradiation, microwave, steam explosion, ammonia fiber explosion (AFEX), supercritical CO2 and its explosion, alkaline hydrolysis, liquid hot-water pretreatment, organosolv processes, wet oxidation, ozonolysis, dilute- and concentrated-acid hydrolyses, and biological pretreatments.

/pdf/pretreatment-of-lignocellulosic-wastes-to-improve-ethanol-zbwx58h962.pdf

Pretreatment of lignocellulosic wastes to improve ethanol and biogas production: a review.

Production of liquid biofuels from renewable resources

Information pertaining to enzymatic hydrolysis of cellulose by noncomplexed cellulase enzyme systems is reviewed with a particular emphasis on development of aggregated understanding incorporating substrate features in addition to concentration and multiple cellulase components. Topics considered include properties of cellulose, adsorption, cellulose hydrolysis, and quantitative models. A classification scheme is proposed for quantitative models for enzymatic hydrolysis of cellulose based on the number of solubilizing activities and substrate state variables included. We suggest that it is timely to revisit and reinvigorate functional modeling of cellulose hydrolysis, and that this would be highly beneficial if not necessary in order to bring to bear the large volume of information available on cellulase components on the primary applications that motivate interest in the subject.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/bit.20282

Toward an aggregated understanding of enzymatic hydrolysis of cellulose: noncomplexed cellulase systems.

Hydrolysis of lignocellulosic materials for ethanol production: a review.

Nutrient recovery from swine lagoon water by Spirodela punctata

A continuous-flow intermittent aeration (IA) process has been studied for nitrogen removal from anaerobically digested swine wastewater with high ammonium content. High nitrogen removal efficiency of average 91% total Kjeldahl nitrogen and 92% NH4-N was achieved in an IA system with an alteration of 1-h aeration and 1-h nonaeration. Nitrification and denitrification were found to be responsible for the nitrogen removal in the system. Nitrite and nitrate in the effluent were less than 1.0 mg/L and 8.0 mg/L, respectively. The specific nitrification and denitrification rates of the single-sludge IA culture were determined through batch experiments as 2.79–3.70 mgNO3-N/g volatile suspended solids-h and 0.59–1.03 mgNO3-N/g volatile suspended solids-h, respectively. In the IA process, the aeration period created favorable conditions for nitrifying bacteria (dissolved oxygen = 4–6 mg/L and oxidation-reduction potential = 80–100 mV), while the nonaeration period provided good environment for denitrifying bacteria...

Nitrification/Denitrification in Intermittent Aeration Process for Swine Wastewater Treatment

Lignocellulosic biomass can be utilized to produce ethanol, a promising alternative energy source for the limited crude oil. There are mainly two processes involved in the conversion: hydrolysis of cellulose in the lignocellulosic biomass to produce reducing sugars, and fermentation of the sugars to ethanol. The cost of ethanol production from lignocellulosic materials is relatively high based on current technologies, and the main challenges are the low yield and high cost of the hydrolysis process. Considerable research efforts have been made to improve the hydrolysis of lignocellulosic materials. Pretreatment of lignocellulosic materials to remove lignin and hemicellulose can significantly enhance the hydrolysis of cellulose. Optimization of the cellulase enzymes and the enzyme loading can also improve the hydrolysis. Simultaneous saccharification and fermentation effectively removes glucose, which is an inhibitor to cellulase activity, thus increasing the yield and rate of cellulose hydrolysis.

Hydrolysis of Lignocellulosic Materials for Ethanol Production: A Review

A mathematical model was developed to describe nitrogen transport in duckweed-covered static ponds for nutrient recovery from swine lagoon water. A finite difference technique was used to solve the partial differential equations describing the ammonia transport and concentration in the pond. The key parameters in the model include the diffusion coefficient of ammonium in the medium (D) and kinetic constant of nitrogen uptake by duckweed (k). Using one order of magnitude parameter variations, the simulations showed that the model was clearly much more sensitive to D than to k, indicating the process of nitrogen removal in a static pond by duckweed is diffusion limited. Laboratory testing was conducted with Spirodela punctata 7776, a duckweed strain, to calibrate the model. The calibration of the model with experimental data yielded a new ammonium transport coefficient (T) that is 85 times of D value. Model results showed good agreement with depth-wise experimental ammonium concentration and the model also ...

Jiayang Cheng

Papers

Hydrolysis of lignocellulosic materials for ethanol production: a review.

Nutrient recovery from swine lagoon water by Spirodela punctata

Nitrification/Denitrification in Intermittent Aeration Process for Swine Wastewater Treatment

Hydrolysis of Lignocellulosic Materials for Ethanol Production: A Review

Modeling Nitrogen Transport in Duckweed Pond for Secondary Treatment of Swine Wastewater